1 /* 2 * linux/arch/arm/mm/mmap.c 3 */ 4 #include <linux/fs.h> 5 #include <linux/mm.h> 6 #include <linux/mman.h> 7 #include <linux/shm.h> 8 #include <linux/sched.h> 9 #include <linux/io.h> 10 #include <linux/personality.h> 11 #include <linux/random.h> 12 #include <asm/cachetype.h> 13 14 static inline unsigned long COLOUR_ALIGN_DOWN(unsigned long addr, 15 unsigned long pgoff) 16 { 17 unsigned long base = addr & ~(SHMLBA-1); 18 unsigned long off = (pgoff << PAGE_SHIFT) & (SHMLBA-1); 19 20 if (base + off <= addr) 21 return base + off; 22 23 return base - off; 24 } 25 26 #define COLOUR_ALIGN(addr,pgoff) \ 27 ((((addr)+SHMLBA-1)&~(SHMLBA-1)) + \ 28 (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1))) 29 30 /* gap between mmap and stack */ 31 #define MIN_GAP (128*1024*1024UL) 32 #define MAX_GAP ((TASK_SIZE)/6*5) 33 34 static int mmap_is_legacy(void) 35 { 36 if (current->personality & ADDR_COMPAT_LAYOUT) 37 return 1; 38 39 if (rlimit(RLIMIT_STACK) == RLIM_INFINITY) 40 return 1; 41 42 return sysctl_legacy_va_layout; 43 } 44 45 static unsigned long mmap_base(unsigned long rnd) 46 { 47 unsigned long gap = rlimit(RLIMIT_STACK); 48 49 if (gap < MIN_GAP) 50 gap = MIN_GAP; 51 else if (gap > MAX_GAP) 52 gap = MAX_GAP; 53 54 return PAGE_ALIGN(TASK_SIZE - gap - rnd); 55 } 56 57 /* 58 * We need to ensure that shared mappings are correctly aligned to 59 * avoid aliasing issues with VIPT caches. We need to ensure that 60 * a specific page of an object is always mapped at a multiple of 61 * SHMLBA bytes. 62 * 63 * We unconditionally provide this function for all cases, however 64 * in the VIVT case, we optimise out the alignment rules. 65 */ 66 unsigned long 67 arch_get_unmapped_area(struct file *filp, unsigned long addr, 68 unsigned long len, unsigned long pgoff, unsigned long flags) 69 { 70 struct mm_struct *mm = current->mm; 71 struct vm_area_struct *vma; 72 unsigned long start_addr; 73 int do_align = 0; 74 int aliasing = cache_is_vipt_aliasing(); 75 76 /* 77 * We only need to do colour alignment if either the I or D 78 * caches alias. 79 */ 80 if (aliasing) 81 do_align = filp || (flags & MAP_SHARED); 82 83 /* 84 * We enforce the MAP_FIXED case. 85 */ 86 if (flags & MAP_FIXED) { 87 if (aliasing && flags & MAP_SHARED && 88 (addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1)) 89 return -EINVAL; 90 return addr; 91 } 92 93 if (len > TASK_SIZE) 94 return -ENOMEM; 95 96 if (addr) { 97 if (do_align) 98 addr = COLOUR_ALIGN(addr, pgoff); 99 else 100 addr = PAGE_ALIGN(addr); 101 102 vma = find_vma(mm, addr); 103 if (TASK_SIZE - len >= addr && 104 (!vma || addr + len <= vma->vm_start)) 105 return addr; 106 } 107 if (len > mm->cached_hole_size) { 108 start_addr = addr = mm->free_area_cache; 109 } else { 110 start_addr = addr = mm->mmap_base; 111 mm->cached_hole_size = 0; 112 } 113 114 full_search: 115 if (do_align) 116 addr = COLOUR_ALIGN(addr, pgoff); 117 else 118 addr = PAGE_ALIGN(addr); 119 120 for (vma = find_vma(mm, addr); ; vma = vma->vm_next) { 121 /* At this point: (!vma || addr < vma->vm_end). */ 122 if (TASK_SIZE - len < addr) { 123 /* 124 * Start a new search - just in case we missed 125 * some holes. 126 */ 127 if (start_addr != TASK_UNMAPPED_BASE) { 128 start_addr = addr = TASK_UNMAPPED_BASE; 129 mm->cached_hole_size = 0; 130 goto full_search; 131 } 132 return -ENOMEM; 133 } 134 if (!vma || addr + len <= vma->vm_start) { 135 /* 136 * Remember the place where we stopped the search: 137 */ 138 mm->free_area_cache = addr + len; 139 return addr; 140 } 141 if (addr + mm->cached_hole_size < vma->vm_start) 142 mm->cached_hole_size = vma->vm_start - addr; 143 addr = vma->vm_end; 144 if (do_align) 145 addr = COLOUR_ALIGN(addr, pgoff); 146 } 147 } 148 149 unsigned long 150 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, 151 const unsigned long len, const unsigned long pgoff, 152 const unsigned long flags) 153 { 154 struct vm_area_struct *vma; 155 struct mm_struct *mm = current->mm; 156 unsigned long addr = addr0; 157 int do_align = 0; 158 int aliasing = cache_is_vipt_aliasing(); 159 160 /* 161 * We only need to do colour alignment if either the I or D 162 * caches alias. 163 */ 164 if (aliasing) 165 do_align = filp || (flags & MAP_SHARED); 166 167 /* requested length too big for entire address space */ 168 if (len > TASK_SIZE) 169 return -ENOMEM; 170 171 if (flags & MAP_FIXED) { 172 if (aliasing && flags & MAP_SHARED && 173 (addr - (pgoff << PAGE_SHIFT)) & (SHMLBA - 1)) 174 return -EINVAL; 175 return addr; 176 } 177 178 /* requesting a specific address */ 179 if (addr) { 180 if (do_align) 181 addr = COLOUR_ALIGN(addr, pgoff); 182 else 183 addr = PAGE_ALIGN(addr); 184 vma = find_vma(mm, addr); 185 if (TASK_SIZE - len >= addr && 186 (!vma || addr + len <= vma->vm_start)) 187 return addr; 188 } 189 190 /* check if free_area_cache is useful for us */ 191 if (len <= mm->cached_hole_size) { 192 mm->cached_hole_size = 0; 193 mm->free_area_cache = mm->mmap_base; 194 } 195 196 /* either no address requested or can't fit in requested address hole */ 197 addr = mm->free_area_cache; 198 if (do_align) { 199 unsigned long base = COLOUR_ALIGN_DOWN(addr - len, pgoff); 200 addr = base + len; 201 } 202 203 /* make sure it can fit in the remaining address space */ 204 if (addr > len) { 205 vma = find_vma(mm, addr-len); 206 if (!vma || addr <= vma->vm_start) 207 /* remember the address as a hint for next time */ 208 return (mm->free_area_cache = addr-len); 209 } 210 211 if (mm->mmap_base < len) 212 goto bottomup; 213 214 addr = mm->mmap_base - len; 215 if (do_align) 216 addr = COLOUR_ALIGN_DOWN(addr, pgoff); 217 218 do { 219 /* 220 * Lookup failure means no vma is above this address, 221 * else if new region fits below vma->vm_start, 222 * return with success: 223 */ 224 vma = find_vma(mm, addr); 225 if (!vma || addr+len <= vma->vm_start) 226 /* remember the address as a hint for next time */ 227 return (mm->free_area_cache = addr); 228 229 /* remember the largest hole we saw so far */ 230 if (addr + mm->cached_hole_size < vma->vm_start) 231 mm->cached_hole_size = vma->vm_start - addr; 232 233 /* try just below the current vma->vm_start */ 234 addr = vma->vm_start - len; 235 if (do_align) 236 addr = COLOUR_ALIGN_DOWN(addr, pgoff); 237 } while (len < vma->vm_start); 238 239 bottomup: 240 /* 241 * A failed mmap() very likely causes application failure, 242 * so fall back to the bottom-up function here. This scenario 243 * can happen with large stack limits and large mmap() 244 * allocations. 245 */ 246 mm->cached_hole_size = ~0UL; 247 mm->free_area_cache = TASK_UNMAPPED_BASE; 248 addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags); 249 /* 250 * Restore the topdown base: 251 */ 252 mm->free_area_cache = mm->mmap_base; 253 mm->cached_hole_size = ~0UL; 254 255 return addr; 256 } 257 258 void arch_pick_mmap_layout(struct mm_struct *mm) 259 { 260 unsigned long random_factor = 0UL; 261 262 /* 8 bits of randomness in 20 address space bits */ 263 if ((current->flags & PF_RANDOMIZE) && 264 !(current->personality & ADDR_NO_RANDOMIZE)) 265 random_factor = (get_random_int() % (1 << 8)) << PAGE_SHIFT; 266 267 if (mmap_is_legacy()) { 268 mm->mmap_base = TASK_UNMAPPED_BASE + random_factor; 269 mm->get_unmapped_area = arch_get_unmapped_area; 270 mm->unmap_area = arch_unmap_area; 271 } else { 272 mm->mmap_base = mmap_base(random_factor); 273 mm->get_unmapped_area = arch_get_unmapped_area_topdown; 274 mm->unmap_area = arch_unmap_area_topdown; 275 } 276 } 277 278 /* 279 * You really shouldn't be using read() or write() on /dev/mem. This 280 * might go away in the future. 281 */ 282 int valid_phys_addr_range(unsigned long addr, size_t size) 283 { 284 if (addr < PHYS_OFFSET) 285 return 0; 286 if (addr + size > __pa(high_memory - 1) + 1) 287 return 0; 288 289 return 1; 290 } 291 292 /* 293 * We don't use supersection mappings for mmap() on /dev/mem, which 294 * means that we can't map the memory area above the 4G barrier into 295 * userspace. 296 */ 297 int valid_mmap_phys_addr_range(unsigned long pfn, size_t size) 298 { 299 return !(pfn + (size >> PAGE_SHIFT) > 0x00100000); 300 } 301 302 #ifdef CONFIG_STRICT_DEVMEM 303 304 #include <linux/ioport.h> 305 306 /* 307 * devmem_is_allowed() checks to see if /dev/mem access to a certain 308 * address is valid. The argument is a physical page number. 309 * We mimic x86 here by disallowing access to system RAM as well as 310 * device-exclusive MMIO regions. This effectively disable read()/write() 311 * on /dev/mem. 312 */ 313 int devmem_is_allowed(unsigned long pfn) 314 { 315 if (iomem_is_exclusive(pfn << PAGE_SHIFT)) 316 return 0; 317 if (!page_is_ram(pfn)) 318 return 1; 319 return 0; 320 } 321 322 #endif 323